Final answer:
The limbic system, including the amygdala and nucleus accumbens, is associated with learning through reinforcement. Studies demonstrate the connection between these structures and reward processing as well as the modulation of learning and behavior by primary and secondary reinforcers.
Step-by-step explanation:
The brain structure shown to be related to learning through reinforcement is the limbic system, which includes critical areas such as the amygdala and the nucleus accumbens. These structures are particularly important in the processing of emotions, memories, and reward. For example, the amygdala is heavily involved in fear conditioning and emotional processing, as suggested by Maren, Phan, & Liberzon (2013), whereas the nucleus accumbens plays a significant role in the reward circuit and has been implicated in motivational aspects of learning, such as in sexual behavior in the research by Everett (1990), Becker, Rudick, & Jenkins (2001), and Jenkins & Becker (2001).
Additionally, the work of Tolman with rats in a maze demonstrates latent learning, where the presence of a goal (food) after a period of unrewarded trials leads to quick learning once the reward is introduced, illustrating the brain's capacity for understanding and utilizing reinforcement once it becomes available. Furthermore, the research performed by Nabavi and others (Nature, 511, 2014), showing how a specific memory was created in a rat through pairing of stimuli, underscores the role of synaptic plasticity in learning which ties in with the principles of reinforcement learning.
Primary and secondary reinforcers are also a key aspect of learning through reinforcement, as exemplified by Skinner's rats in the Skinner box, where food was used as a primary reinforcer to shape behavior. Humans similarly learn behaviors through conditioning using both types of reinforcers, with rewards varying based on the context and individual needs as highlighted in the studies by Daniel & Esser (1980) and Rushworth et al. (2011).